Spinal implant and method for fabricating the same

ABSTRACT

A spinal implant is provided that includes a body extending in direction at least substantially along a body axis, between a first end portion and a second end portion. The spinal implant also includes a first bearing surface disposed relative to the first end portion, and defining a first relief pattern that is configured to inhibit movement of the spinal implant relative to one or more vertebrae in at least substantially all directions. A method for manufacturing the spinal implant involves use of selective laser sintering.

CROSS-REFERENCE TO RELATED APPLICATION

The present disclosure claims priority to U.S. Provisional PatentApplication No. 62/039,148, filed Aug. 19, 2014, which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a medical interbody implant, and morespecifically relates to a spinal implant that defines a bearing surfaceconfigured to inhibit movement of the implant relative to one or moreadjacent vertebra and to promote fusion of the adjacent vertebra to thespinal implant. The present invention further relates to a method ofmanufacturing a spinal implant, and more specifically a method of usingselective laser sintering to manufacture a spinal implant having thebearing surface.

BACKGROUND OF THE INVENTION

Spinal fusion is a surgical technique in which a spinal implant is usedto join one or more vertebrae. In preparation for the spinal fusion, theone or more intervertebral discs between the vertebrae are removed. Thespinal implant is surgically inserted between the vertebrae in order tomaintain spine alignment and intervertebral disc height. FIG. 1, forexample, illustrates a prior art spinal implant 1 inserted betweenadjacent first and second vertebrae 2, 3. The spinal implant can be madefrom various different materials, including, for example, a plasticand/or a metal (e.g., titanium). After the spinal implant is surgicallyinserted between the vertebrae, the vertebrae fuse with bearing surfacesdefined on opposing ends of the spinal implant. The fusion processtypically takes between 6 to 12 months after surgery. The post-surgeryfusion process can be augmented by the placement of screws, rods,plates, and/or cages related to one or more of the vertebrae in order tostabilize the vertebrae and facilitate bone fusion.

A disadvantage of known spinal implants is that external forces cancause a movement (also known as “slippage” or “floating”) of the spinalimplant relative to one or more of the vertebrae. The likelihood of sucha translation is particularly high during the period between 6 to 12months after surgery, when the fusion process typically takes place.Such movement is disadvantageous, because the positioning of the spinalimplant relative to the vertebrae requires a high degree of precision inorder to provide the desired therapeutic effect. Any unwanted movementcan negatively impact any therapeutic and any benefit to the patient.

It is known to form a relief pattern on one or more bearing surfaces ofthe spinal implant in an attempt to inhibit movement of the spinalimplant relative to a vertebra in a direction extending parallel and/orperpendicular to a bearing surface of the vertebra. FIG. 2, for example,illustrates a prior art spinal implant 1 having a top bearing surface 4that defines a plurality of linear grooves and ridges 5 in the topbearing surface 4 of the prior art spinal implant 1. The grooves andridges 5 aid in inhibiting movement of the spinal implant 1 relative toa vertebra (not shown) in a widthwise direction extending perpendicularto the grooves and ridges 5. However, the grooves and ridges 5 do notinhibit movement of the spinal implant 1 relative to a vertebra (notshown) in a lengthwise direction extending parallel to the grooves andridges 5 or in other directions parallel to a plane defined by the topbearing surface 4. FIG. 3 illustrates another prior art spinal implant 1having a top bearing surface 4 that defines a plurality of pyramids 6extending therefrom. The pyramids 6 aid in inhibiting movement of thespinal implant 1 relative to a vertebra (not shown) in alengthwise-extending direction in which opposing first and second faces7 a, 7 b of the pyramid 6 are directed, and a widthwise-extendingdirection in which opposing third and fourth faces 7 c, 7 d of thepyramid 6 are directed. However, the pyramids 6 do not inhibit movementof the spinal implant 1 relative to the vertebra in other directionsparallel to a plane defined by the bearing surface 4, or in aheightwise-extending vertical direction relative to the plane.

Aspects of the present invention are directed to these and otherproblems.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a spinal implant isprovided that includes a body extending in direction at leastsubstantially along a body axis, between a first end portion and asecond end portion. The spinal implant also includes a first bearingsurface disposed relative to the first end portion, and defining a firstrelief pattern that is configured to inhibit movement of the spinalimplant relative to one or more vertebrae in at least substantially alldirections.

According to another aspect of the present invention, a method formanufacturing a spinal implant is provided that includes the step ofselective laser sintering a body extending in direction at leastsubstantially along a body axis, between a first end portion and asecond end portion, and having a first bearing surface disposed relativeto the first end portion, the first bearing surface defining a firstrelief pattern that is configured to inhibit movement of the spinalimplant relative to one or more vertebrae in at least substantially alldirections.

In addition to, or as an alternative to, one or more of the featuresdescribed above, further aspects of the present invention can includeone or more of the following features, individually or in combination:

-   -   the spinal implant further includes second bearing surface        disposed relative to the second end portion, and defining a        second relief pattern that is configured to inhibit movement of        the spinal implant relative to one or more vertebrae in at least        substantially all directions;    -   the first bearing surface defines a plurality of protrusions        integrally connected therewith, and extending therefrom, which        collectively define the first relief pattern;    -   the plurality of protrusions each have an at least generally        conical shape, and each defining a base integrally connected to        the first bearing surface, and a tip at a distal end of the        respective protrusion;    -   the base defines a base width, the tip defines a tip width, and        the base width is greater than the tip width;    -   at least one of the plurality of protrusions is configured such        that the tip overhangs the base;    -   at least one of the plurality of protrusions has a hook-like        conical shape;    -   the tip is truncated, blunted, and/or rounded;    -   the base defines a tapered and/or convex surface that provides a        smooth and/or rounded transition between the surface of the        respective protrusion and the first bearing surface;    -   each of the plurality of protrusions extends along a protrusion        axis that passes through an apex of the respective protrusion;    -   at least one of the plurality of protrusions is oriented        obliquely relative to the first bearing surface;    -   the plurality of protrusions define a plurality of angles        between the respective protrusions and the first bearing        surface;    -   the respective angles are randomly selected to be within a        predetermined range of angles;    -   the plurality of protrusions are oriented in a plurality of        different directions relative to the body axis;    -   the respective orientations are randomly selected;    -   each of the plurality of protrusions extends along a protrusion        axis that passes through an apex of the respective protrusion;        and the respective protrusion axes extend in generally all        directions towards and/or away from the body axis;    -   the body defines a plurality of side surfaces extending        substantially perpendicular to the first bearing surface between        the first end portion and the second portion of the body; and        the respective protrusion axes of the plurality of protrusions        intersect with respective planes defined by each of the        plurality of side surfaces at a plurality of positions on the        respective planes;    -   the plurality of protrusions define a plurality of heights        extending between their respective tips and the first bearing        surface;    -   the respective heights are randomly selected;    -   the respective heights of the plurality of protrusions is        between 1 mm and 3 mm;    -   the selective laser sintering step involves using a laser to        selectively fuse a polymeric powder material;    -   the polymeric powdered material is a polyaryletherketone        (“PAEK”) powder material; and    -   the PAEK powder material includes at least one material selected        from the group consisting of: polyetheretherketone (“PEEK”),        polyetherketone ketone (“PEKK”), polyetherketone (“PEK”),        polyetheretherketoneketone (“PEEKK”) or        polyetherketoneetherketoneketone (“PEKEKK”).

These and other aspects of the present invention will become apparent inlight of the drawings and detailed description provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a human spine with a prior artspinal implant.

FIG. 2 illustrates a perspective view of another prior art spinalimplant.

FIG. 3 illustrates a perspective view of another prior art spinalimplant.

FIG. 4 illustrates a front elevation view of a first embodiment of thepresent spinal implant.

FIG. 5 illustrates a perspective view of the spinal implant of FIG. 4.

FIG. 6 illustrates a perspective view of the top end portion of thespinal implant of FIG. 4.

FIG. 7 illustrates a plan view of the top end portion of the spinalimplant of FIG. 4.

FIG. 8 illustrates a front elevation view of the top end portion of thespinal implant of FIG. 4.

FIG. 9 illustrates a side elevation view of the top end portion of thespinal implant of FIG. 4.

FIG. 10 illustrates a plan view of the bottom end portion of the spinalimplant of FIG. 4.

FIG. 11 illustrates a perspective view of the top end portion of asecond embodiment of the present spinal implant.

FIG. 12 illustrates a side elevation view of the top end portion of thespinal implant of FIG. 11.

FIG. 13 illustrates a perspective view of the top end portion of a thirdembodiment of the present spinal implant.

FIG. 14 illustrates a plan view of the top end portion of a fourthembodiment of the present spinal implant.

FIG. 15 illustrates a front elevation view of the top end portion of thespinal implant of FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 4-15, the present disclosure describes a spinalimplant 10, and a method for manufacturing the spinal implant 10.

The present disclosure describes aspects of the present invention withreference to the exemplary embodiments illustrated in the drawings;however, aspects of the present invention are not limited to theexemplary embodiments illustrated in the drawings. The presentdisclosure may describe one or more features as having a lengthextending relative to an x-axis, a width extending relative to a y-axis,and/or a height extending relative to a z-axis. The drawings illustratethe respective axes.

Referring to FIGS. 4 and 5, the spinal implant 10 includes a firstbearing surface 12 and a second bearing surface 14 positioned atopposing ends of the spinal implant 10. The first and second bearingsurfaces 12, 14 each define a relief pattern that is configured toinhibit movement of the spinal implant 10 relative to one or morevertebrae in at least substantially all directions. The present spinalimplant 10 thus offers significant advantages over prior art spinalimplants, which only prevent such movement in some directions.

The spinal implant 10 includes a body 16 that: (ii) extends in alengthwise direction between a first side surface 18 and a second sidesurface 20; (iii) extends in a widthwise direction between a frontsurface 22 and a rear surface 24; and (iii) extends in a heightwisedirection between a first end portion 26 and an opposing second endportion 28 at least substantially along a body axis 30. The firstbearing surface 12 is disposed relative to the first end portion 26, andthe second bearing surface 14 is disposed relative to the second endportion 28. The distance between the first and second end portions 28,30 is equal to or less than approximately 3 inches.

The first and second bearing surfaces 12, 14 each define a plurality ofprotrusions 32 integrally connected therewith, and extending therefrom,which collectively define the respective relief patterns of the firstand second bearing surfaces 12, 14.

Referring to FIGS. 8 and 12, the protrusions 32 each have an at leastgenerally conical shape. The protrusions 32 each define a base 34integrally connected to the respective bearing surface 12, 14, and a tip36 at a distal end of the protrusion 32. The base 34 defines a basewidth 38, and the tip 36 defines a tip width 40. The base width 38 isgreater than the tip width 40.

In some embodiments (see FIGS. 4-12 and 14-15), the tip 36 of eachprotrusion 32 is truncated, blunted, and/or rounded. In some embodiments(see FIGS. 6, 8, 9, etc.), the base 34 of each protrusion 32 defines atapered or convex surface that provides a smooth and/or roundedtransition between the surface of the protrusion 32 and the respectivebearing surface 12, 14 with which it is integrally formed.

In some embodiments (see, e.g., FIG. 13), at least one of theprotrusions 32 is configured such that the tip 36 of the protrusion 32overhangs the base 34 of the protrusion 32. That is, the tip 36 of theprotrusion 32 passes through a plane extending perpendicular to therespective bearing surface 12, 14 at the perimeter of the protrusionbase 34. In some of these and other embodiments, the protrusions 32 canhave a tooth-like or hook-like conical shape. In such embodiments, theprotrusions 32 can effectively form a “hook” that can engage a vertebrain an interlocking event, which can thereby inhibit relative movement ofthe spinal implant 10 relative to the vertebra along an axis at leastsubstantially perpendicular to the respective bearing surface 12, 14 ofthe spinal implant 10.

Referring to FIGS. 6, 8, and 11-13, the protrusions 32 each extend alonga protrusion axis 42 that passes through the apex of the protrusion 32.One or more of the protrusions 32 are oriented obliquely relative to therespective bearing surface 12, 14 with which they are integrally formed.That is, the respective protrusion axes 42 are disposed at one or morenon-parallel and non-perpendicular angles 44 relative to the body axis30.

Referring to FIGS. 8 and 12, in some embodiments, the protrusions 32 ona respective bearing surface 12, 14 can define a plurality of differentangles 44 between the respective protrusion axes 42 and the respectivebearing surface 12, 14. In such embodiments, the angles 44 of theprotrusions 32 can be randomly selected (e.g., by a drafting program orthe like), or can have the appearance of being randomly selected, withina predetermined range (e.g., between 10° and 80°).

Referring to FIGS. 6, 11, 13, and 14, in some embodiments, theprotrusions 32 on a respective bearing surface 12, 14 can be oriented ina plurality of different directions relative to the body axis 30. Insome embodiments, the respective protrusion axes 42 collectively extendin generally all directions towards and/or away from the body axis 30.In some embodiments, the respective protrusion axes 42 intersect withthe respective planes defined by each of the first side surface 18, thesecond side surface 20, the front surface 22, and the rear surface 24 ofthe body 16 at a plurality of different lengthwise, widthwise, and/orheightwise positions on the respective planes. In such embodiments, theorientation of the protrusions 32 can be randomly selected (e.g., by adrafting program or the like), or can have the appearance of beingrandomly selected.

Referring to FIGS. 8, 12, and 15, the protrusions 32 each define aheight 46 equal to the distance extending between the respective bearingsurface 12, 14 and the tip 36 of the respective protrusion 32 in adirection at least substantially parallel to the body axis 30. Theheights 46 of the protrusions 32 can vary depending on the procedure forwhich the spinal implant 10 is to be used, one or more physiologicalfacts of the patient (e.g., sizes of the patient's vertebrae), and/orone or more other design considerations. In some embodiments, forexample, the heights 46 of the protrusions 32 are between 1 mm and 3 mm.In some embodiments (see FIGS. 8 and 12), the protrusions 32 all havesubstantially the same height 46. In other embodiments (see FIG. 15),the respective protrusions 32 of at least one of the first and secondbearing surfaces 12, 14 have a plurality of different heights 46 a, 46b. In such embodiments, the different heights 46 can be achieved byvarying the height at which one or more of the protrusions 32 aretruncated, blunted, and/or rounded. The different heights 46 canadditionally or alternatively be achieved by providing the base 34 ofone or more of the protrusions 32 with a different shape relative to thebases 34 of the other protrusions 32 on the respective bearing surface12, 14, and/or by providing one or more protrusions 32 with a differentangle 44 relative to the other protrusions 32 on the respective bearingsurface 12, 14. In some embodiments, the protrusions 32 can have heights46 that are randomly selected (or that have the appearance of beingrandomly selected) to be with a predetermine height range (e.g., 1 mm to3 mm).

In some embodiments, including the illustrated embodiments, the body 16of the spinal implant 10 includes an aperture 48 extending between thefirst and second bearing surfaces 12, 14.

In some embodiments, a known fixation device (not shown) can be used toprevent movement of the spinal implant 10 relative to one or morevertebrae.

The cost and logistics of manufacturing a spinal implant 10 havingprotrusions 32 as described above (e.g., with tips 36 that overhang thebases 34) makes conventional manufacturing techniques (e.g., subtractivemanufacturing techniques, machining, etc.) impossible. Accordingly, amethod for manufacturing the spinal implant 10 involves use of selectivelaser sintering (SLS), which is an additive manufacturing technique thatuses electromagnetic radiation from a laser to fuse small particles ofpowders into a mass that has a desired three-dimensional shape.

The present method involves the following steps, the order of which canvary: (i) using a laser to selectively fuse powdered material byscanning two-dimensional cross-sections according to a three dimensionaldigital description of the part (also known as a “build file”) on thesurface of a powder bed; (ii) after a cross-section is scanned, loweringthe powder bed by one layer thickness; (iii) applying a new layer ofmaterial; and (iv) rescanning the powder bed. Steps (i)-(iv) arerepeated until the desired three-dimensional shape part is completed.

The powder bed used in the method includes a polymeric powder material,including, for example, a polyaryletherketone (“PAEK”) powder material.PEAK powder materials are particularly useful here because they arecharacterized by a low flammability, a good biocompatibility, and a highresistance against hydrolysis and radiation. The thermal resistance atelevated temperatures as well as the chemical resistance distinguishesPAEK materials from ordinary plastic powders. A PAEK powder material caninclude be one or more powder materials selected from the groupconsisting of polyetheretherketone (“PEEK”), polyetherketone ketone(“PEKK”), polyetherketone (“PEK”), polyetheretherketoneketone (“PEEKK”)or polyetherketoneetherketoneketone (“PEKEKK”).

In some embodiments, it can be especially advantageous to use a PEKKpowder material, available under the brand name OXPEKK® from OxfordPerformance Materials, Inc. in South Windsor, Conn. Specimens fabricatedfrom OXPEKK® polymer have been subjected to biocompatibility testingaccording to ISO 10993 and USP <85> standards, and have met allapplicable criteria for devices with permanent bone and tissue bodycontact with the additional potential to contact the cerebrospinalfluid. Such test specimens have been subjected to a successfulsterilization validation. It should be understood that there aredifferent blends of PEKK powder materials. Unlike other PAEK materials,PEKK is a copolymer (AB type EKK/EKK). The examples described hereinpertain to the 60/40 PEKK copolymer sold under brand name OXPEKK®. Itshould be understood, however, that the present invention is not limitedto any specific blend of PEKK resin, and that different blends may beused.

In embodiments in which the method involves an unused PEKK powdermaterial, the method can additionally or alternatively include one ormore of the following steps, the order of which can vary: (a) verifyingthat that the unused PEKK powder material is adequately dry; (b) loadingthe unused PEKK powder material into a SLS machine; (c) loading the PEKKpowder material is loaded into a hopper, or the like, from which an SLSmachine can distribute sequential layers of powder onto a powder bed ofthe SLS machine for sintering; (d) loading the part geometries (alsoknown as the “build definition”) into a computer associated with the SLSmachine; (e) pre-heating the SLS machine according to known methods; (f)setting the bed temperature to a temperature as determined bycharacterization of the PEKK powder material; (g) setting the laserpower to a power specified by the vendor and/or to a power determinedfrom earlier runs of the SLS process; (h) setting a powder layerthickness (e.g., 125 microns); (i) after the layer-wise build isperformed, cooling the resulting powder cake at a controlled rate (e.g.,between 1 and 100 degrees Celsius per hour); (j) after powder cake hasachieve at least substantially room temperature, removing the spinalimplant 10 therefrom. Regarding step (i), it should be appreciated by aperson having ordinary skill in the art that the rate of cooling dependson the dimensions of the cake, with deeper beds typically requiring moretime to cool.

While several embodiments have been disclosed, it will be apparent tothose of ordinary skill in the art that aspects of the present inventioninclude many more embodiments and implementations.

Accordingly, aspects of the present invention are not to be restrictedexcept in light of the attached claims and their equivalents. It willalso be apparent to those of ordinary skill in the art that variationsand modifications can be made without departing from the true scope ofthe present disclosure. For example, in some instances, one or morefeatures disclosed in connection with one embodiment can be used aloneor in combination with one or more features of one or more otherembodiments.

What is claimed is:
 1. A spinal implant, comprising: a body extending indirection at least substantially along a body axis, between a first endportion and a second end portion; a first bearing surface disposedrelative to the first end portion, and defining a first relief patternthat is configured to inhibit movement of the spinal implant relative toone or more vertebrae in at least substantially all directions.
 2. Thespinal implant of claim 1, further comprising a second bearing surfacedisposed relative to the second end portion, and defining a secondrelief pattern that is configured to inhibit movement of the spinalimplant relative to one or more vertebrae in at least substantially alldirections.
 3. The spinal implant of claim 1, wherein the first bearingsurface defines a plurality of protrusions integrally connectedtherewith, and extending therefrom, which collectively define the firstrelief pattern.
 4. The spinal implant of claim 1, wherein the pluralityof protrusions each have an at least generally conical shape, and eachdefining a base integrally connected to the first bearing surface, and atip at a distal end of the respective protrusion.
 5. The spinal implantof claim 4, wherein the base defines a base width, the tip defines a tipwidth, and the base width is greater than the tip width.
 6. The spinalimplant of claim 4, wherein at least one of the plurality of protrusionsis configured such that the tip overhangs the base.
 7. The spinalimplant of claim 4, wherein at least one of the plurality of protrusionshas a hook-like conical shape.
 8. The spinal implant of claim 4, whereinthe tip is truncated, blunted, and/or rounded.
 9. The spinal implant ofclaim 4, wherein the base defines a tapered and/or convex surface thatprovides a smooth and/or rounded transition between the surface of therespective protrusion and the first bearing surface.
 10. The spinalimplant of claim 4, wherein each of the plurality of protrusions extendsalong a protrusion axis that passes through an apex of the respectiveprotrusion.
 11. The spinal implant of claim 4, wherein at least one ofthe plurality of protrusions is oriented obliquely relative to the firstbearing surface.
 12. The spinal implant of claim 11, wherein theplurality of protrusions define a plurality of angles between therespective protrusions and the first bearing surface.
 13. The spinalimplant of claim 12, wherein the respective angles are randomly selectedto be within a predetermined range of angles.
 14. The spinal implant ofclaim 4, wherein the plurality of protrusions are oriented in aplurality of different directions relative to the body axis.
 15. Thespinal implant of claim 14, wherein the respective orientations arerandomly selected.
 16. The spinal implant of claim 14, wherein each ofthe plurality of protrusions extends along a protrusion axis that passesthrough an apex of the respective protrusion; and wherein the respectiveprotrusion axes extend in generally all directions towards and/or awayfrom the body axis.
 17. The spinal implant of claim 16, wherein the bodydefines a plurality of side surfaces extending substantiallyperpendicular to the first bearing surface between the first end portionand the second portion of the body; and wherein the respectiveprotrusion axes of the plurality of protrusions intersect withrespective planes defined by each of the plurality of side surfaces at aplurality of positions on the respective planes.
 18. The spinal implantof claim 4, wherein the plurality of protrusions define a plurality ofheights extending between their respective tips and the first bearingsurface.
 19. The spinal implant of claim 18, wherein the respectiveheights are randomly selected.
 20. The spinal implant of claim 1,wherein the respective heights of the plurality of protrusions isbetween 1 mm and 3 mm.
 21. A method for manufacturing a spinal implant,comprising: selective laser sintering a body extending in direction atleast substantially along a body axis, between a first end portion and asecond end portion, and having a first bearing surface disposed relativeto the first end portion, the first bearing surface defining a firstrelief pattern that is configured to inhibit movement of the spinalimplant relative to one or more vertebrae in at least substantially alldirections.
 22. The method of claim 21, wherein the selective lasersintering step involves using a laser to selectively fuse a polymericpowder material.
 23. The method of claim 22, wherein the polymericpowdered material is a polyaryletherketone (“PAEK”) powder material. 24.The method of claim 23, wherein the PAEK powder material includes atleast one material selected from the group consisting of:polyetheretherketone (“PEEK”), polyetherketone ketone (“PEKK”),polyetherketone (“PEK”), polyetheretherketoneketone (“PEEKK”) orpolyetherketoneetherketoneketone (“PEKEKK”).